The present disclosure relates generally to orthopedic spine surgery and specifically to unique retractor devices and surgical methods to perform orthopedic spine surgery by way of a minimally open or less invasive approach.
There has been considerable development of retractors and retractor systems for less invasive spine surgery procedures, with most of the new technologies being based on traditional types of surgical retractors for open procedures, predominantly table-mounted devices of various designs. These prior devices are large and bulky and frequently are not well suited to the smaller incisions and muscle sparing approaches desired for less invasive surgery. Most retractor systems may be classified as table mounted systems, handheld systems, and soft tissue anchored systems. Table-mounted systems generally contain a retractor attached to a surgical table through a support arm. As appreciated by one skilled in the art, the design of table-mounted systems is bulky and provides a user with limited degree of maneuverability. Standard handheld surgical retractors are well known and can be modified to fit the contours of these smaller incisions, but they require manual manipulation to maintain position during surgery. Soft tissue anchored systems are positioned into the soft tissue and levered back to hold the wound open, frequently requiring re-positioning when they dislodge or obstruct the view or access pathways. The table mounted systems, handheld systems, and soft tissue anchored systems are all susceptible to displacement in numerous directions as a result of pressure exerted on the patient's body caused by, among other things, the surgeon's work within the body or the patient's breathing. The pressure exerted on the patient's body causes a reactionary force on the retractor and may displace the retractor from its original location.
There is, therefore, a demonstrated need for a retractor which can be self-retaining in the incision, can be fixed so as to inhibit dislodgement, does not require re-positioning yet allows for manual manipulation which increases the surgeon's procedural flexibility and is minimally obtrusive so as to not interfere with the surgical procedure.
Furthermore, the retractor should provide a protected working channel to access the disc space. To that end, it would be advantageous if the retractor could be expanded medially to increase visualization and exposure without enlarging the incision. Finally, a retractor device that is simple to introduce as well as remove will increase the likelihood of its use.
In recent years, minimally open surgical approaches have been applied to orthopedic spine surgery and, more recently, to spine fusions involving one or more vertebral bodies. Unlike minimally invasive procedures such as arthroscopic knee surgery or gallbladder surgery where the affected area is contained within a small region of the body, spine surgery involving a fusion typically spans a considerably larger length or portion of the body. For this reason, the idea of performing a minimally open procedure on the spine has only recently been approached.
By way of example, a typical spine fusion in the lumbar region, whereby at least two vertebral bodies are rigidly connected using screws implanted into the vertebral body and a rod spanning the distance between the screws is by its nature not very conducive to a minimally open approach. Furthermore, a spine fusion is typically supported by implanting one or more interbody devices into the disc space either using an anterior or posterior approach. An anterior approach requires a separate incision whereby the surgeon accesses the patient's spine through the abdomen. One advantage of the anterior approach is that the interbody used in this procedure closely matches the footprint of the adjacent vertebral bodies. The disadvantage is that an anterior procedure is typically performed at a different time and requires its own incision and access.
A posterior approach to interbody implantation can be achieved through the same incision as that of the pedicle screws. Implantation of a Posterior Lumbar Interbody Fusion (PLIF) device requires bilateral removal of the facet joints and requires introduction and implantation of two bilateral implants. A Transforaminal Lumbar Interbody Fusion (TLIF) approach can be achieved unilaterally and may require removal of only one facet joint. Another advantage of the TLIF approach is that only one device is implanted into the disc space
While the implantation of pedicle screws can be achieved with relatively little site preparation, interbody implantation requires considerable access and surgical implant site preparation by the surgeon. Once the facet joint is removed, the surgeon can begin removing the disc. One or more instruments may be needed to access the site at any time as well as sufficient lighting and suction. To perform these tasks, the surgeon needs a suitable opening or channel to work through.
Several minimally open or minimally invasive access devices currently exist to achieve the goal of a suitable working channel. Most are either mounted to the surgical table or held in place by the surgeon or an assistant. Table mounted retractors offer little flexibility. Furthermore, such retractors do not offer a relationship or positional guidance with respect to the patient.
Handheld retractors provide greater flexibility but require an extra hand to maintain position. They also may or may not offer a fixed relationship to the patient but in either case can easily be knocked out of position. Furthermore, handheld retractors typically offer a very long and narrow fixed channel to work through making the procedure even more challenging. Several handheld retractors have been developed over the years. For example, U.S. Pat. No. 6,849,064 describes a handheld access system that has the ability to expand muscle tissue. To this end, this access system includes hinged bi-hemispherical or overall working tubes applied over an obturator that is controllably dilated to separate muscle tissue slowly.
Scientists have also developed soft tissue anchored retractors. These retractors are typically anchored to the patient's soft tissue rather than a table. As such, soft tissue anchored retractors offer the surgeon more flexibility than table mounted retractors but less flexibility than handheld retractors. There are different kinds soft tissue anchored retractors. U.S. Pat. No. 5,503,617 discloses a soft tissue anchored retractor for direct access endoscopic surgery. This retractor includes a rigid frame capable of supporting the applied loads required to perform retraction of an incision site. The rigid frame includes a handle at one end and a lower blade mount rotatably connected to the opposite end. A translation frame is slidably connected to the rigid frame and includes an upper blade mount rotatably connected thereto. Lower and upper blades are removably mounted on the lower and upper blade mounts, respectively.
Finally, any of the above-mentioned retractors typically require a form of dilation to obtain the initial opening. Circular or oblong dilators are well known in the art, but do not provide flexibility in configuring the desired access corresponding to the encountered anatomy. In addition, sequentially dilating tissue to make an opening large enough to perform surgery through the dilator or to accept a retracting device is tedious and can be traumatic to the patient. A retracting device that reduces or eliminates the steps associated with dilator devices would be advantageous. Minimally open surgery offers significant advantages over conventional open surgery. At the onset, the skin incision and subsequent scar are significantly smaller. A truly minimally open spine procedure should constitute the smallest damage or disruption possible to the surrounding anatomy. While there may be one or more incisions, depending on the number of levels needing attention, the amount of muscle and vascular retraction and scraping should be reduced to result in less operative trauma for the patient. A minimally open procedure also is likely to be less expensive, reduce hospitalization time, cause less pain and scarring, reduce the incidence of complications and reduce recovery time.